In processing a raw material of agricultural, marine and livestock products into dry powder, the conventional process comprises the process steps as shown in the flow chart of FIG. 1. In the process steps of slicing of the raw material, primary drying, gas injection treatment for improving the product quality and preservation effect, crushing, spraying addition of a liquid additive for improving the product quality and preservation effect, re-drying and dispersive mixing, or in the process steps of slicing, drying and crushing of the raw material, for the production of a dry pulverous product, the following problems are encountered:
1) A large number of devices and instruments have to be employed due to separate furnishment of each individual device and instrument for each unit operation together with the requisite insertion of handling arrangements and cushioning tanks between them. PA1 2) The operation of such a large number of devices and instruments is bothersome with annoying maintenance works. PA1 3) It requires a higher investment cost and a larger installation area for accomodating such a large number of devices and instruments. PA1 4) A larger costs are required for the administration of operation of the apparatuses. PA1 5) A deterioration of the product quality due to air oxidation is incidental to the process steps of cutting and slicing, handling and crushing of the raw material. PA1 6) Due to the extended period for each processing of the handling and drying, the productivity is low with facilitated deterioration of the product quality. PA1 7) A product quality deterioration due to the heat generation upon the crushing operation occurs. PA1 8) The processing instruments and devices will be stained by deposition and clinging of the processed material during the handling operations after the spraying of the liquid additives. PA1 9) Since the injection of the processing gas is carried out in general at ordinary pressure, there is some difficulty in its sufficient permeation into the interior of the material being processed. PA1 placing the food raw material in a closed vessel, PA1 subjecting the material to chopping or cutting while evacuating the vessel to a vacuum, PA1 effecting drying of the so-cut material and PA1 crushing the resulting cut material.